OMAP3+: voltage: remove initial voltage

Blindly setting 1.2V in the initial structure may not even match the
default voltages stored in the voltage table which are supported for
the domain. For example, OMAP3430 core domain does not use 1.2V and
ends up generating a warning on the first transition.

Further, since omap2_set_init_voltage is called as part of the pm
framework's initialization sequence to configure the voltage required
for the current OPP, the call does(and has to) setup the system
voltage(curr_volt as a result) using the right mechanisms appropriate
for the system at that point of time. This also overrides
initialization we are currently doing in voltage.c making it
redundant. So, remove the wrong and redundant initialization.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>